Over on another forum (EEVBLOG), there's a REALLY good thread going on "how transistors work" that is more detailed than "it's an amplifier" and less detailed than "Starting with the state equation of an electron in a quantum well..." In particular, read the posts by "free_electron": How transistors…

How transistors work...

Topic		Replies	Views
What are transistors. General Electronics	55	11220	May 6, 2021
Programmer branching out, where to begin? General Electronics	7	1113	May 6, 2021
What is a Transistor? General Electronics	10	2991	May 6, 2021
Understanding Transistors General Electronics	26	6997	May 6, 2021
Still can't get my head around what a transistor does General Electronics	13	4441	May 6, 2021